The overall goal of this study is to improve the effectiveness of programs to prevent mother-to-child HIV transmission (PMTCT) in resource-limited countries through the piloting and further development of an intervention aimed at addressing adherence to PMTCT and early care of HIV-infected women and their children. It is now well recognized that the many PMTCT programs that have been established worldwide are not performing optimally in preventing HIV infection among children and have failed in their potential to be entry points for care for HIV-infected women and their children. The success of a PMTCT program requires adherence to many different activities: e.g., performance of a CD4 count in early pregnancy and maintenance of safe infant feeding. This research uses an intervention that is based in social-ecological theory and uses participatory methods to improve adherence to the multiple components of PMTCT by affecting the behaviors of the participants (administrators, staff and patients) so as to bring about structural changes in the health care system and change the behaviors of individuals. The aims of the study are to: 1. Implement the intervention in a single health care sub-district in South Africa comprised of 11 antenatal clinics and three hospitals and assess the extent to which the intervention improves different components of PMTCT by using readily available health department data to examine changes over time in markers of adherence to PMTCT (i.e. proportion with CD4 tests and PCR testing of children). 2. Conduct a qualitative evaluation to assess the acceptability and feasibility of the intervention and identify factors that either impede or facilitate implementation. 3. Conduct a quantitative evaluation to examine the extent to which there is change in each of the activities involved in PMTCT, identify variables that have a mediating effect and determine to what extent these are modified by the intervention. This will be done by analyzing data obtained from two different cohorts of HIV positive women -- the first will have received their antenatal care prior to implementation of the intervention, and the second cohort will be women attending antenatal care after the intervention has been introduced. HIV positive women will be enrolled at the time of delivery and data on adherence to PMTCT will be obtained in follow-up interviews at three months. The interviews will include information on adherence to care and factors that might contribute to adherence (e.g.: disclosure of HIV status and quality of the patient-provider relationship). Quantitative analyses will be performed to determine differences in PMCTC-related activities and identify variables that have a mediating effect on improving outcomes. The qualitative evaluation will contribute to further development of the intervention. Following completion of this study, the intervention will be implemented more widely, its effectiveness assessed, and efforts made to ensure widespread dissemination. PUBLIC HEALTH RELEVANCE: In limited-resource countries efforts to prevent mother-to-child transmission of HIV and ensure appropriate care for HIV-infected women and their children presently fall short of their potential. The goal of this research is to further develop an intervention to improve adherence to care for HIV-infected women in pregnancy and post- delivery. With future demonstration of the efficacy of this intervention and further dissemination, the intervention developed in this research could have a substantial impact on improving the health of HIV-infected women and their children and prevent high rates of death in early infancy.